Modular structural composite beam

ABSTRACT

A modular fiber reinforced plastic flange for a structural composite beam which comprises a body formed of a plurality of elongate elements arranged in an array, wherein the dimensions of the body are substantially determined by the number and arrangement of the elongate elements in the array, and a skin member at least partially surrounding the array. Also, a structural composite beam comprising the modular fiber reinforced plastic flange and a shear web connected to the skin member of the modular flange. A method of making the modular flange and beams, and a kit of parts for making the modular flange are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Patent Cooperation TreatyInternational Patent Application PCT/GB2011/000661, filed Apr. 28, 2011,and entitled “A MODULAR STRUCTURAL COMPOSITE BEAM,” which isincorporated by reference herein in its entirety, and which claimspriority to Great Britain Patent Application 1007336.9, filed on Apr.30, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a modular structural composite beam. Inparticular, the present invention relates to a modular structuralcomposite beam for use in a wind turbine blade.

2. Description of the Related Art

Large wind turbine blades (>35 m in length) are typically constructed byforming a strengthening and stiffening cantilever beam or box sparinside an aerodynamic fairing. The current approach to manufacturingwind turbine blades is to produce each blade either as two half shellswith a separate beam, or as two half shells with an integral beam. Inboth cases, the two half shells are bonded together along their edges toform the complete blade.

The structural beam comprises flanges at either end which are connectedto one another by one, or more commonly two, shear webs. The flanges aremade from predominantly unidirectional fibre reinforced plastic and theshear webs consist of predominantly multi-axial (+/−45°) fibrereinforced plastic.

It is well known in the art to make the beam by moulding the flangeswithin the half shells of the aerodynamic fairing and then bonding theflanges together with the shear webs when the aerodynamic fairings arejoined together. Alternatively the beam is made by moulding a separatebeam on a separate tool and then bonding the beam into the aerodynamicfairings when they are joined together.

These methods each have a number of shortcomings. Firstly, if theunidirectional flange of the beam is moulded within the fairing it isdifficult to accurately control the quality of the flange material. Thistypically results in poor mechanical properties from the flange materialleading, in turn, to increased mass required for engineering safety andtherefore increased cost.

If the beam is made separately by moulding on a separate tool some ofthe above shortcomings may be avoided. However, the cost of the separatetool adds to the overall cost of the component.

In either case, if a new design or a slight variation in design isrequired, completely new tools need to be made thereby increasingprototyping time and cost also increasing the cost introducing newmodels. Similarly, if the use of automation is considered, the cost ofautomation will be high since then it must be capable of dealing with anumber of different beam designs and geometries.

SUMMARY OF THE INVENTION

A design for a modular wind turbine blade is described in theapplicant's published International patent application WO 2009/034291.This application discloses a wind turbine blade which comprises aplurality of standardised component parts which allow for greater designflexibility, for the blade as a whole, than traditional manufacturetechniques. However, it only provides limited options for modificationof the structural beam design. It is an aim of the present invention toprovide a modular structural composite beam which provides improveddesign flexibility and quality and which can be used as part of atraditional wind turbine blade, as part of a modular wind turbine blade,or in other structural applications such as bridges.

Accordingly, in a first aspect the present invention provides a modularfibre reinforced plastic flange for a structural composite beamcomprising: a body formed of a plurality of elongate elements arrangedin an array such that the longitudinal axes of the elongate elements aresubstantially parallel to one another, wherein the dimensions of thebody are substantially determined by the number and arrangement of theelongate elements in the array; and a skin member at least partiallysurrounding a plurality of the elongate elements in the array.

By constructing the body of the flange from a plurality of elongateelements with an outer skin the design of the flange can be readilyvaried by varying the size and configuration of the array of elongateelements and skin member. The provision of a skin member also providesimproved shear load performance.

In a preferred embodiment the skin member fully surrounds the array ofelongate elements to provide additional support and structuralintegrity.

The skin member preferably comprises first and second skin elements, thefirst skin element having a concave form and the second skin elementbeing arranged to fit within the first skin element. This arrangementallows the body to be placed in the first skin element before the secondskin element is fitted to complete the skin member. In this way thethickness of the body can be varied with little, or no, variation thedimensions of the skin member.

Preferably the skin member comprises a socket to receive, in use, ashear web. This provides a convenient method of attaching the flange tothe shear web and transferring loads between the flange and shear web.

In a preferred embodiment at least two of the elongate elements comprisedifferent materials. This allows the mechanical properties of the flangeto be readily varied.

In order to further improve the shear load performance, at least onereinforcement layer is preferably at least partially located within thearray of elongate elements.

In a second aspect, the present invention provides a structuralcomposite beam comprising: a modular flange according to the firstaspect of the invention; and a shear web connected to the skin member ofthe modular flange. In this way an improved and more versatilestructural composite beam is provided.

The shear web preferably comprises a structural core located between twocomposite material layers to provide further structural integrity. Thecomposite material layers are preferably multiaxial composite material.The shear web is advantageous as it can be assembled into the flange asan ‘open’ sandwich panel as the panel is terminated by the socket of theskin member. This means that the shear web(s) can be made in acontinuous production process as opposed to a discrete moulding process(which would otherwise be required to ‘close’ the ends of the sandwichpanel), thereby reducing production costs and increasing flexibility.

In a third aspect, the present invention provides a method of forming amodular fibre reinforced plastic flange for a structural composite beamcomprising: forming a body from a plurality of elongate elementsarranged in an array such that the longitudinal axes of the elongateelements are substantially parallel to one another, wherein thedimensions of the body are substantially determined by the number andarrangement of the elongate elements in the array; and connecting a skinmember to the body such that the skin member at least partiallysurrounds a plurality of the elongate elements in the array.

The method preferably further comprises: selecting a number andarrangement of elongate elements to define the dimensions of the body;and selecting a skin member which is sized to substantially fit thedimensions of the body. In this way flanges of varying dimensions andmechanical properties can be readily formed from standardised componentswithout the need to re-tool.

Preferably the skin member comprises first and second skin elements, thefirst skin element having a concave form and the second skin elementbeing arranged to fit within the first skin element; the method furthercomprising: locating the body within the first skin element; andlocating the second skin element within the first skin element to form askin member which fully surrounds the body.

In a fourth aspect, the present invention provides a method of forming astructural composite beam comprising: using the method of the thirdaspect of the invention; and connecting at least one shear web to theskin member of the modular flange.

Preferably in the method of the third aspect of the invention, or in themethod of the fourth aspect of the invention each component part of themodular flange or structural composite beam is made in a continuousproduction process. This reduces production costs and improves qualitysince continuous production processes are less time and labour intensiveand more repeatable thereby reducing waste.

Before the methods of the third or fourth aspects of the invention arecarried out, the elongate elements and skin member of the modularflange, and the at least one shear web of the structural composite beam,are preferably in a cured or semi-cured state and exhibit their finalform. Thus, the shape and dimensions of the elongate elements, skinmember and shear webs are substantially fixed before the modular flangeor structural composite beam is assembled. In addition, the principalmechanical properties of the elongate elements, skin member and shearwebs are substantially fixed before the modular flange or structuralcomposite beam is assembled.

In a fifth aspect, the present invention provides a kit of parts forforming modular fibre reinforced plastic flanges comprising: a pluralityof elongate elements suitable for forming a body comprising a pluralityof elongate elements arranged in an array wherein the longitudinal axesof the elongate elements are substantially parallel to one another; anda plurality of skin members, wherein the plurality of skin members aresized to correspond to predetermined multiples of elongate elements. Thekit thereby provides means for producing flanges of varying sizes andmechanical properties.

The elongate elements and skin members of the kit of parts arepreferably in a cured or semi-cured state and exhibit their final form.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the present invention will now be described with referenceto the following drawings in which:

FIG. 1 shows an exploded schematic view of part of a modular structuralcomposite beam;

FIG. 2 shows a schematic sectional view of a modular fibre reinforcedplastic flange and separate webs;

FIG. 3 shows a schematic sectional view of part of an assembled modularstructural composite beam;

FIG. 4 shows a schematic sectional view of part of an alternativeassembled modular structural composite beam; and

FIG. 5 shows a schematic sectional view of part of a further alternativeassembled modular structural composite beam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows an exploded schematic view of a section of a modularstructural composite beam 10. The beam 10 comprises first 20 and second30 skin elements and a plurality of elongate elements 40. In addition,the beam 10 comprises two shear webs 50 each comprising a structuralcore 52 and outer skin layers 54.

The structural cores 52 may be made of any suitable material includingPVC, PET, balsa wood or STYROFOAM or other structural core materialwidely known and used in the art. The outer skin layers 54 comprisepredominantly multiaxial (±45°) fibre reinforced plastic. The outer skinlayers 54 are attached to the cores 52 by an adhesive such as astructural adhesive (such as epoxy, polyurethane, acrylic, silicone) orwith a resin such as a polyester, vinylester, epoxy or other structuralthermosetting or thermoplastic resin.

The elongate elements 40 comprise predominantly uniaxial fibrereinforced plastic. The elongate elements are typically ‘preformed’unidirectional composite materials such as pulltrusions or semi-curedprepreg or intermediate types of materials such that they exhibit theirfinal shape or form before the flange 5 (see FIG. 2) is formed. As shownin FIG. 1, the elongate elements 40 are arranged in an array, in thiscase a three by three array, to form a body 42 which forms the main loadbearing component of the flange 5. The elongate elements 40 are adheredtogether to form the body 42 either by structural adhesive or bylaminating together with structural resin using a process such as handlaminating, vacuum infusion, vacuum consolidation or similar laminatingprocesses used in the art.

The first and second skin elements 20, 30 each comprise predominantlymultiaxial fibre reinforced plastic. The first skin element 20 has aU-shaped concave form and the second skin element 30 comprisesprojections 32 which define sockets 34 at each outer edge of the secondskin element 30. The sockets 34 are sized to receive the edges 56 of theshear webs 50.

As shown in FIG. 2, in the assembled flange 5 the second skin element 30fits within the first skin element 20. Together the two skin elements20, 30 form skin member 60 which fully surrounds the body 42. In thisexample, ‘fully surrounds’ means that the skin member 60 encircles thebody 42 but does not cover the ends of the body 42.

As is also shown in FIG. 2, the first and second skin elements 20, 30are sized to fit the body 42. The dimensions of the body 42 are definedby the number and arrangement of elongate elements in the array. In theexample shown in FIG. 2, the body 42 comprises a three by three arraysuch that the depth of the body 42 is substantially the same as threetimes the depth of the elongate elements 40, and the width of the body42 is substantially the same as three times the width of the elongateelements 40.

FIG. 3 shows the flange 5 assembled together with the shear webs 50. Theshear webs fit into the sockets 34 and are attached by means of anadhesive such as a structural epoxy adhesive. As shown, location of theshear webs 50 in the sockets 34 ‘closes’ the ends of the shear webs 50.In FIG. 3 only the upper section of a box beam 10 is shown. It will beappreciated that another flange 5 can be attached to the lower side ofthe shear webs 50 to form the complete box beam 10. In addition, theshear webs 50 can be of various depths to vary the depth of the box beam10. This depth can be varied along the length of the beam to account,for example, for the taper of a wind turbine blade.

FIG. 4 shows an alternative configuration of an upper section of amodular structural composite beam 100. In this case the beam 100 is anI-beam comprising only one shear web 50 located in a central socket 134of second skin member 130. The elongate elements 40, 140 which form thebody 142 of the flange 105 comprise different fibre reinforced plasticmaterials such that elongate elements 40 may comprise, for example,glass fibre reinforce plastic, and elongate elements 140 may comprise,for example, carbon fibre reinforced plastic. The arrangement of thedifferent material elongate elements 40, 140 shown is FIG. 4 is anexample only and any other arrangement may be selected depending of themechanical properties desired.

The beam 100 further comprises reinforcement layers 144 located betweenthe layers of elongate elements 40, 140 in the body 42. Thesereinforcement layers comprise predominantly multiaxial (±45°) fibrereinforced plastic and provide additional shear strength to the flange105. Reinforcement layers 144 may be included in any of the modularstructural composite beam configurations described herein.

FIG. 5 shows a further alternative configuration of an upper section ofa modular structural composite beam 200. elongate elements 40 and theskin member 260 comprises only a single skin element 220 which partiallysurrounds elongate elements 40 a, 40 b and 40 c of the array.

It will be appreciated that any number of elongate elements 40, 140 maybe included in the array which forms the body 42, 142, 242, and anynumber of different fibre reinforced plastic materials in any desiredarrangement may be selected for the elongate elements. In this way themechanical properties of the flange 5, 105, 205 may be varied asdesired.

Referring again to FIG. 2, if the width of the body 42 stays the same(three elongate elements wide) but the depth changes (for example, twoelongate elements deep) the same skin elements 20, 30 can be used sincethe difference in depth is accommodated by the fact that the second skinelement 30 fits into the first skin element 20 until it reaches the body42. If desired, the sides 22 of the first skin element 20 may be trimmedto remove the overlap with the projections 32 of the second skin element30. Alternatively, a greater depth body 42 (for example, four or moreelongate elements deep) can be accommodated by the variable depthcapability provided by the interaction of the first and second skinelements 20, 30. In this case the projections 32 of the second skinelement 30 may optionally be trimmed to remove the overlap with thesides 22 of the first skin element 20.

If the width of the body 42 varies (for example, two elongate elementswide) it is desirable to provide skin elements 20, 30 of a suitable sizeto fit the width of the body 42. The elongate elements 40 preferablyhave standard dimensions so that a set of standardised sizes of skinelements 20, 30 can be provided to fit various different arrays ofelongate elements.

The fibre reinforced plastic components described above are typicallyglass fibre reinforced plastics or carbon fibre reinforced plastics asare well known in the art. However any other suitable fibre reinforcedplastic material may be used.

What is claimed is:
 1. A modular fibre reinforced plastic flange for astructural composite beam comprising: a modular body formed of aplurality of pre-cured elongate elements each formed from a compositematerial, the elongate elements having rectangular cross-sections andextending longitudinally the length of the beam, the elongate elementsbeing arranged side-by-side, on top of one another, or side-by-side andon top of one another in an array such that the longitudinal axes of theelongate elements are substantially parallel to one another, wherein thedimensions of the modular body are determined by the number andarrangement of the elongate elements in the array; and a pre-curedplastic modular skin member comprising a first skin element and secondskin element, the first skin element having a rectangular concavecross-section, the second skin element being sized to join with thefirst skin element to securely contain the array of elongate elementstherein, the first and second skin elements being configurable toaccommodate a variable number and arrangement of elongate elements inthe array, and the modular skin member extending longitudinally along asubstantial portion of the length of a plurality of the elongateelements in the array.
 2. A modular flange as claimed in claim 1,wherein the skin member fully surrounds the array of elongate elements.3. A modular flange as claimed in claim 2, wherein the second skinelement is arranged to fit within the first skin element.
 4. A modularflange as claimed in claim 1, wherein the skin member comprises a socketto receive, in use, a shear web.
 5. A modular flange as claimed in claim1, wherein at least two of the elongate elements comprise differentmaterials.
 6. A modular flange as claimed in claim 1, further comprisingat least one reinforcement layer at least partially located within thearray of elongate elements.
 7. A structural composite beam comprising: amodular flange as claimed in claim 1; and a shear web connected to theskin member of the modular flange.
 8. A structural composite beam asclaimed in claim 7, wherein the shear web comprises a structural corelocated between two composite material layers.
 9. A method of forming amodular fibre reinforced plastic flange for a structural composite beamcomprising: forming a modular body from a plurality of elongate elementseach formed from a composite material, the elongate elements havingrectangular cross-sections and extending longitudinally the length ofthe beam, the elongate elements being arranged side-by-side, on top ofone another, or side-by-side and on top of one another in an array suchthat the longitudinal axes of the elongate elements are parallel to oneanother, wherein the dimensions of the modular body are substantiallydetermined by the number and arrangement of the elongate elements in thearray; and connecting a plastic modular skin member to the body, theskin member comprising a first skin element and second skin element, thefirst skin element having a rectangular concave cross-section, thesecond skin element joining with the first skin element to securelycontain the array of elongate elements therein, the first and secondskin elements being configurable to accommodate a variable number andarrangement of elongate elements in the array, and the modular skinmember extending longitudinally along a substantial portion of thelength of a plurality of the elongate elements in the array, wherein theelongate elements and skin member of the modular flange are in a curedor semi-cured state and exhibit their final form before forming thebody.
 10. A method of forming a modular flange as claimed in claim 9,further comprising: selecting a number and arrangement of elongateelements to define the dimensions of the body; and selecting a skinmember which is sized to substantially fit the dimensions of the body.11. A method of forming a modular flange as claimed in claim 10, whereinthe second skin element is arranged to fit within the first skinelement; the method further comprising: locating the body within thefirst skin element; and locating the second skin element within thefirst skin element to form a skin member which fully surrounds the body.12. A method of forming a structural composite beam comprising: usingthe method of claim 9 to form a modular flange; and connecting at leastone shear web to the skin member of the modular flange.
 13. A method offorming a modular flange as claimed in claim 9, wherein each componentpart of the modular flange is made in a continuous production process.14. A method of forming a structural composite beam as claimed in claim12, wherein each component part of the structural composite beam is madein a continuous production process.
 15. A method as claimed in claim 12,wherein, before forming the body, the at least one shear web of thestructural composite beam is in a cured or semi-cured state and exhibitsits final form.
 16. A kit of parts for forming modular fibre reinforcedplastic flanges comprising: a plurality of elongate elements each formedfrom a composite material, the elongate elements having rectangularcross-sections and extending longitudinally the length of a beam, theelongate elements being suitable for forming a modular body comprisingthe plurality of elongate elements arranged side-by-side, on top of oneanother, or side-by-side and on top of one another in an array, whereinthe longitudinal axes of the elongate elements are parallel to oneanother; and a plurality of plastic modular skin members, wherein theplurality of skin members are sized to correspond to predeterminedmultiples of elongate elements, each skin member comprising a first skinelement having a rectangular concave cross-section and a second skinelement being sized to join with the first skin element to securelycontain the array of elongate elements therein the first and second skinelements being configurable to accommodate a variable number andarrangement of elongate elements in the array, and each modular skinmember extending longitudinally along a substantial portion of thelength of thereof, wherein the elongate elements and skin members are ina cured or semi-cured state and exhibit their final form.